This building was since the early phases of the project planned to maximize the solar gains into the building through the windows facing south. The envelope of the building is external insulated, with 5 cm thick in a single masonry wall and has 10 cm insulation on the roof. The building has a solar thermal system to assist the auxiliary heating system, for the winter season when necessary. In fact, this auxiliary system has been used very rarely mainly in the north part of the building in periods with a sequence of days with no sun. In the heating season, the heat produced in the PV system in the fa? ade is recovered by natural convection to heat the south facing rooms.

1.1. Winter thermal performance

During these two year monitoring campaign (February 2006 until February 2008) the building showed a very good thermal behaviour in the south part of the building, where the mean temperatures varies between a mean minimum of 17°C to a mean maximum of 24°C. In the north part of the building, the temperature are a quite bite lower than in the south part of the building, 1 to 2°C, which consequently imply the use of some auxiliary heat source. Table 1 presents the mean values for the winter months, and it is very important to see that during daytime (Tdaily) the mean temperatures are always above 20°C.

Figure 3 presents the hourly temperatures, in the 3 levels of the building, for the coldest month in winter (January 2007), where it is possible to see that during day time the temperatures are always above 20°CC, except days 9, 10, 11, 17 of January where some extra heating was needed.